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  1. they usually distort when battery is low

    they usually distort when battery is low
  2. Replies
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    418

    All the 2000 series amps have heating problems on...

    All the 2000 series amps have heating problems on the bridge rectifier for the preamp tubes filaments,it is mounted with no clearance from the board,the heating causes soldering cracks.
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    252

    you need to figure out the primary impedance of...

    you need to figure out the primary impedance of the OT,and the plate and screen grid voltages coming out of the supply,then it's possible to do some math or use a loadline calculator,there are some...
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    187

    i would clean very well tube sockets with ipo...

    i would clean very well tube sockets with ipo alcohol,both on top and on the pcb side,then check out the bias circuit for any instability,for good measure i would replace the pot,that is very...
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    258

    that's the main resistor,between first and second...

    that's the main resistor,between first and second filter capacitor,if that is not connected no power no signal.
    Try to solder it adding fresh solder.
    Do you think the soldering broke because of...
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    258

    yes, resistors need soldering,which one is it?

    yes, resistors need soldering,which one is it?
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    253

    It's an SLO,just undo all the mods, check out the...

    It's an SLO,just undo all the mods, check out the gain pots, sometimes they wear out and short.
  8. negative feedback iirc

    negative feedback iirc
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    330

    put that 470k in series with the bright cap

    put that 470k in series with the bright cap
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    495

    just got it sorted out right now,it was a broken...

    just got it sorted out right now,it was a broken path from the s3 switch to the chip, pins 9 and 16,too many vias,replaced with a straight wire directly.
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    495

    just got a MIC recent Bandit,service manual is...

    just got a MIC recent Bandit,service manual is the one from 2007,same problem,channel chip is stuck in clean mode
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    1,107

    what about filament voltage? some amps have a...

    what about filament voltage?
    some amps have a reduction in standby
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    303

    no problem with 100uF,the other smaller ones are...

    no problem with 100uF,the other smaller ones are for the preamp,once you have changed the main ones its better to energize the amp with a variac or a simple bulb limiter to reduce the high voltage...
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    191

    most of the time its not even the bridge...

    most of the time its not even the bridge itself,but the fact that heating up in direct contact with the board the soldering crack,and you get no voltage.
    I had success replacing the bridge with a 10...
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    259

    99% of the time you will find cathode bias amps...

    99% of the time you will find cathode bias amps running at least 90% of dissipation and up,like Voxes which go up to 130%.
    Is it right?
    I won't go in class A or AB explanations,it is like that and...
  16. Replies
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    1,651

    filter caps if original,its time to go,also check...

    filter caps if original,its time to go,also check the rectifier tube and any resistor on the power supply string
  17. another thing that is peculiar to that channel is...

    another thing that is peculiar to that channel is the vibrato pot always attached to the third stage,if you disconnect that probably you will get a fuller sound.
    But Fender ab763 are not flat by...
  18. Replies
    11
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    707

    that thing shouldn't cost more than 15...i have...

    that thing shouldn't cost more than 15...i have one...it has less power than a good soldering station and the sucking pressure is not that great ,especially after it starts to clog up.
    If you plan...
  19. Try finding nos European tubes,I never had...

    Try finding nos European tubes,I never had problems like this.
  20. Replies
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    697

    You want to double the impedance to match the 2...

    You want to double the impedance to match the 2 power tubes, but you need to measure turn ratios anyway before making choices.
  21. almost every 4 stage amp has a snubber on third...

    almost every 4 stage amp has a snubber on third stage anode resistor,or a couple smaller on 2nd and third,that's good measure in preventing oscillations.
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    868

    i would check the OT out of circuit for...

    i would check the OT out of circuit for mismatched wiring
  23. no scope i imagine... best thing to do first is...

    no scope i imagine...
    best thing to do first is to disconnect all wires from the amp to test the OT.
    One thing you can do is feeding a low ac voltage to the secondary taps and check the primary...
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    1,167

    the first triode passes on the signal to the...

    the first triode passes on the signal to the second one through the cathode connection,which comes out in phase to the plate,that's your inversion of the first triode,then you have the feedback...
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    1,476

    nope,the cfx one has discrete transistors in CFP...

    nope,the cfx one has discrete transistors in CFP configuration,the fan spins only when it gets too hot,i repaired one reflowing some solderings,lead free is the best you know....
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    456

    probably filter caps went short and pulled too...

    probably filter caps went short and pulled too much current,that heated up the choke windings,going short,then HV secondary.
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    456

    filament heater secondary not referenced to...

    filament heater secondary not referenced to ground or missing one of the 100 ohm resistor?
    power tubes ok?
    screen resistors?
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    i would use one type only,whatever it is....

    i would use one type only,whatever it is.
    Increase performance,which way?
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